Radio transmission system



Dec. 29, 1925. I

' R. A. HElSlNG RADIO TRANSMISSION SYSTEM Filed 001:. 1. 1919' //1 ven for Raymond/I. fievsmy. fly

Fig. 2.

Patented 1)....29, 1925.-

UNITED STATES PATENT OFFICE.

RAYMOND A. HEISING, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, NEW YORK.

or NEW YORK, N. Y., a-coarona'rron on RADIO TRANSMISSION SYSTEM.

Application filed October 1,1919 Serial No. 327,744.

sion systems and more particularly to du-v plex radio communication systems.

The general object of the invention is to provide improved means of and methods for duplex radio transmission.

A particular object is to provide a system wherein transmission can be carried on at one wave length and reception at another wave length, choice of several Wave lengths being available for reception irrespective of which wave length is being used for transmission and vice versa.

A further object is to provide a system which can be so balanced that transmission and reception can be carried on at a variety of combinations of wave lengths without readjusting the balance.

A further object is to provide efficient and practical means whereby the transmitting and receiving wave lengths may be independently changed. a

A further object is to provide a novel form of network for balancing the impedance of an antenna particularly for balancing the antenna at several wave lengths.

Additional objects of the invention will be apparent to those skilled in the art from a perusal of the following detailed description. I

Fig. 1 of the accompanying drawings is a dia rammatic representation of a system embo ying the invention, Figs. 2 and 2 are diagrams hereinafter referred to in conneotion with-the explanation of the duplex balance of the system; and Fig. 3 shows a preferred manner of winding the antenna 7 Fig. 1 illustrates a station .of a du lex radio system wherein aradiatingcon no tor 1 is connected to ground through a coil 2 and a balancing network N. A condenser ma in-some instances be included in series wit the conductor 1 to increase the capacitive reactance thereof. A variable capacity 4 is shunted around the coil 2 for a reason hereinafter stated. The coil 2 is wound in a particular manner hereinafter described. The conductor 5 contains'or-is suitably associated with a source of signaling waves to be transmitted. In the present instance this source is the means connected with the coil 6 in which is induced an electromotive force corresponding/to a high frequency wave modulated in accordance with speech waves. A-condenser 7 may be rovided to give the conductor 5 a desire reactance. The means for inducing suitable electromotive forces in coil 6 comprises any suitable system S which in the present instance consists of a high frequency oscillator' O of the thermionic type. Oscillator 0 comprises a vacuum tubeS having in its grid clrcuit a coil 9 coupled to coil 6 and blocking condenser 10, the coil 9 and condenser 10 bein shunted by a resistance leak ath 11. he plate circuit of tube 8 inclu es condenser 12 in series with the parallel arrangement ofcoil 13 and the vari-- able condenser 14, the coil 13 being coupled to coil 6. The function of the condenser 14 is to vary the effective. coupling of the coil 13 to the coil 6. Coils 9 and 13 are so arranged that the directmutual inductance therebetween is negligible. The anodecathode current of tube 8' is provided from source 15 through the speech frequency choke coil 16. shunted around tube -8 is the anode-cathode path 17 of tube 18. vThe impedance of tube 18 is varied in accordance with s eech waves by providing a circuit 19 in which speech frequency waves are produced and couplin the circuit 19 to the inut circuit 20 oft e tube 18 by the speech requency transformer 21. Between the negative terminal of the source 15 and the cathodes 22 of the tubes 8 and 1'8'is'connected a resistance 23v and a condenser 24 in shunt thereto. .The 'total'space current for tubes '8 and 18 passes throu h resistance 23, hence by connectingthe gri element 25 of tube 18' to the negative terminal of resistance 23, the grid 25 is maintained at a suitable negative potential 'with respect to its cooperating cathode. The resistance 23 may be -of any value which will give the most efficient operation. of sufficient ca acity to be of low. impedance to such;

Condenser 24 isv uctuating potentials as are impressed across resistance 23. Since the total current through resistance 23 is approximately constant, the normal potential on grid 25 will be substantially constant.

The network or artificial antenna comprises a variable inductance in series with the combination of a variable resistance shunted by a-variable inductance and also in series with a variable condenser. This form ofnetwork is of peculiar utility in that it will not only balance the antenna for one wave length but may be adjusted togive a very exact balance at two wave lengths and a fairly accurate balance over a considerable range of wave lengths. This is illustrated in Fig. 2, where the effective capacity of an ordinary type of antenna, plotted against wave length corresponds over a certain. range of values to the curve a,-wh1le the effective capacity of a condenser having a small inductance in series similarly plotted corresponds to a curve having the form n. By proper adjustment the two curves may be made to cross each other at two selected wave lengths, for example, 190 and 315 meters. Then at other wave lengths such as 150, 230, 270 and meters the unbalance will be comparatively slight. It is further illustrated in Fig. 2* where the effective resistance of an ordinary type of antenna plotted against wave length is represented by the curve a and the effective resistance of an inductance and resistance, such as inductance 80 and resistance 31 in parallel, is shown by the curve 41'. By properly choosing these values the two curves may be made to approximately coincide over a certain range of wave lengths, as, for example, from 150 to 360 meters, which may be taken as the range over which operation is to be carried on. By combining this parallel combination with the condenser 32 and the inductance 33, as shown in Fig. 1, the behavior of effective capacity and the effective resistance as a .function of the wave length. as shown in Figs. 2 and 2*, can be made to occur. The network contains four variables, and by properly adjusting them the network can be made to give at the wave lengths represented by the points I) and c the same effective capacity and the same effective resistance as occur in the real antenna. Over the desired operating range the departure of the actual antenna efl'ective capacity and resistance curves from those of the network will be so small as not to interfere seriously enough with the balance to cause trouble in operating the set. The two points 6 and 0 corresponding to 190 and 315 meters respectively at which the most accurate balance occurs may in part, for instance by proper adjustment, be made to fallv at suchother wave lengths other than 190 and 315 meters as may be desired.

momma into the conductor 5 will be negligible if the coefficient of coupling between the parts of coil 2'is approximately unity. The coefiicient of coupling between the two parts of the coil is caused-to be approximately unity by winding the parts 2 and 2" with their turns closely. adjacent. The operating requirement is that the total ampere turns of the parts of the coil be equal. This is most simply accomplished by making the number of turns in the parts of the coil equal. Approximately one-half of the generated power is' then wasted in the network N. For short range sets this is no serious diiiiculty. For higher power sets for lon range work, the coil 2 may be so designed and the network N so adjusted that a much smaller amount than one-half of the power is wasted in the network N. The impedance of the network will then be high, care being taken to see that the power factor of the network is equal to that of the antenna.

The receiving set R comprises a tuned or other suitable selective circuit 27 coupled to the coil 2 in such a manner that the minimum effectof the outgoing energy is impressed upon the circuit 27. This may be accomplished under ordinary circumstances by giving coil 28 in circuit 27 a single adjustment in its spatial relation to coil 2 which will be suited for all combinations "of wavelengths to be utilized. The circuit 27 comprises the input circuit of a detec' tor D. An amplifier A is provided to amplify the detected current and transfer the energy to any suitable signal indicating device 29. Suitable shielding is provided as shown in dotted lines so that capacity to ground variations will not disturb the balance.

. In operation the coil 6 is varied to cause the transmitted wave to be of a suitable length, this being determined in general by the natural frequency of the conductor 5 in series with the parallel branches comprising the antenna and the artificial antenna. The condenser 4 may be varied to tune the antenna for reception. The length of the transmitted wave is wholly independent of the capacity of the condenser 4 since potent-ialsrimpressed on conductor 5 will cause no difference of potential across the condenser 4. if the balance is exact. and only a negligible difference of potential if the proportionately balance is slightly imperfect. 'Thus it is possible to transmit on any oneof several wave lengths and have available any one of several wave lengths for reception. Either the transmitting or the receiving wave length may be changed at-any time. Transmission and reception may be carried on either simultaneously or successively and it is possible to receive from one station while transmitting to one or more others.

The novel features which are believed to be inherent in the invention are defined in the appended claims.

' IVhat I claimed is:

1. A duplex radio station comprising a radiatory antenna and an artificial antenna for balancing said radiatory antenna. said artificial antennacomprising a capacity in series with a parallel arrangement of inductance and resistance. i

2. An artificial antenna comprising a variable inductance in series'with a variable capacity and the combination of a variable resistance in parallel with a second variable inductance.

3. In a radio system, a radiating circuit, a balancing circuit therefor including an element having chiefly resistive impedance at radio frequencies, and an element shunted around said first named element having chiefly inductive impedance at radio frequencies.

4. A duplex} radio system comprising an aerial, separate and inde endent tuning means for transmission an reception, and a network comprising impedance elements simulating the impedance of, said aerial over a wide range of frequencies whereby, with a fixed and invariable ad'ustment of said elements, either the transmitting or receiving frequencies may be varied over a considerable frequency range by means of one of said tuning means, with a minimum of interference with the frequency established by the other tuning means.

5. A duplex radio station. com rising a radiating member, a path from sai member to ground through a closed circuit containing an inductance and a capacity, and through an artificial antenna, and a branch path to ground from an intermediate point on said inductance.

6. A duplex radio system comprising a transmitter and a receiver, a circuit for transmission and reception and a variable tuning condenser for reception connected across points of said circuit across which said transmitter sets up, only negligible differences of potential.

7. In a duplex radio system an aerial member for radiating the outgoing and absorbing incoming wave energy, a balancing member for said aerial member, an inductance element connecting said balancing member with said aerial member, a connection from an intermediate portion of said element to ground through a path connected to transmitting means, a capacity for tuning received waves shunted around said element and a receiver coupled to said element.

8. In a duplex radio system a enerating system for producing waves an varying them in accordance with signals, a path connected to said. system and connected to the middle point of a divided im edance element, a receiver equally couple to the parts of said divided impedance element, and tunin reactance means shunted around the impe ance element for tuning for received waves.

9. In a duplex radio s stem a transmitting sourcesof waves, equeney varying means associated therewith, two paths to be traversed by waves from said source, said paths being oppositely cou led to a receiver circuit, and tuning means or reeeivlng connected across similar portions of said paths whereby the operation of said transmitting source at any frequency of waves to be transmitted sets up only negligible differences of potential across said tuning means.

In witness whereof, I hereunto subscribe my name this 27th day of September, A. D.,

RAYMOND A. HEISING. 

